It has been known in the past to utilize small magnetic elements to mix blood drawn into collection tubes for clinical testing with an anticoagulant, normally a heparin salt, which coats the interior surfaces of the tubes. The ferromagnetic element or slug is simply inserted into the bore of the tube after a blood sample has been taken and the element is then shifted back and forth within the tube under the direction of an external magnet manipulated by the technician. Following such a mixing operation, the magnetic element is extracted from the tube by means of the magnet, and is then separated from the magnet and discarded or washed for re-use. Danger lies in the fact that considerable difficulty is often encountered in performing such steps without direct contact between the sample blood and the technician's fingers. Such contact is practically inevitable if the magnet and/or the mixing element are to be washed and re-used. Since the blood may indeed have one or more of the pathological conditions for which it is intended to be tested, and since at least some of those conditions are highly infectious (serum hepatitis, for example), it is apparent that any direct contact between the user and the sample blood involves serious risks and should be avoided. Despite such risks, an effective and dependable solution to these problems has been wanting.
In view of the difficulties involved in removing the blood-coated magnetic elements from such collection tubes or in separating the contaminated elements from the reusable magnets, without risking direct finger contact with the sample blood, some users either omit the magnetic mixing step completely or leave the magnetic elements within the collection tubes following the mixing step. Should the mixing step be completely omitted, the sample blood may become coagulated and either preclude proper testing or render the results meaningless or misleading. On the other hand, should a magnetic element be left within a collection tube, whether accidentally or intentionally, the ferromagnetic element is likely to be drawn into and obstruct the flow circuit of an automatic analyzer, possibly causing serious damage to its intricate system and requiring costly, time-consuming repairs.
This invention involves the discovery of a relatively simple but highly effective solution to such problems. All of the advantages of the magnetic mixing procedure may be realized without the risks of contamination previously associated with that procedure. Specifically, by the method and combination of this invention it is now possible to perform magnetic mixing in a blood collection tube and thereafter capture, remove, and discard the magnetic slug or mixing element without danger of direct contact between the blood sample and a user's fingers.
Briefly, the system involves the use of at least one elongated tubular cap as the means for sealing one (or both) ends of a blood collection tube. In the best form known for practicing the invention, such a cap should be resilient and be provided with an elongated tapered cavity having a mouth portion for snugly but removably receiving an end of the collection tube and having a main cavity portion extending beyond that tube when the cap is in place. The length and diameter of the interior of the cap exceed the corresponding dimensions of the magnetic element or slug used for mixing blood and anticoagulant within the collection tube. However, once the magnetic element is fully received within the cap, the opposite wall portions of that cap may be squeezed together by the user's fingers to hold the magnetic element within the cavity of the cap. Without changing the positions of his fingers, the user then simply detaches the cap from the collection tube and, with the blood-coated collection tube captured within the cavity, the cap and magnetic elements are discarded together. Since the cap initially forms a fluid-tight seal with the collection tube, and since that seal is not disturbed until after the blood-coated magnetic element is fully received within the cavity of the cap and securely held in place therein, the dangers of direct contact between the sample blood and the technician's fingers during such an operation are eliminated or at least greatly reduced.
Other advantages, features, and objects of the invention will become apparent from the specification and drawings.